The purpose of this proposed research is to study the formation of urinary stones in experimental animals and the metabolic alterations responsible for their production. The studies will be divided into 3 parts. The production of apatite and calcium oxalate stones in rats fed diets containing lactose will be investigated. The production of calcium oxalate renal stones in monkeys will be studied and the effect of dietary purines on stone formation in monkeys and rats will be evaluated. Finally, hydroxyproline will be studied as a precursor of urinary oxalate and urinary stones.